Introducing UnitsDB 1.0
We are pleased to announce the first stable release of UnitsDB — the authoritative, machine-readable database of scientific units of measure.
UnitsDB 1.0 provides a comprehensive, structured dataset covering the SI system and widely used non-SI units. Every entity is identified by both a NIST identifier and a human-readable short name, making the database useful for both reference and programmatic access.
What's in the database
UnitsDB 1.0 ships with data across five entity types, all authored in YAML for easy reading and editing:
| Type | Count |
|---|---|
| Units | 380+ |
| Quantities | 180+ |
| Dimensions | 84 |
| Prefixes | 33 |
| Unit Systems | 5 |
Units
The units dataset covers SI base units (meter, kilogram, second, ampere, kelvin, mole, candela), SI derived units (newton, pascal, joule, watt, volt, hertz, and many more), and non-SI units accepted for use with SI (minute, hour, day, degree, liter, tonne, and others).
Each unit entry includes:
- Identifiers — NIST ID and short name
- Dimension reference — linking to the corresponding dimension
- Quantity references — quantities this unit measures
- System membership — which unit systems the unit belongs to
- Root unit decomposition — how derived units relate to base units
Quantities
Physical quantities like length, mass, time, force, energy, and pressure, each typed as either base or derived and linked to their dimension.
Dimensions
SI base quantity dimensional powers (L, M, T, I, Θ, N, J) defining the dimensional analysis framework.
Prefixes
All 33 SI decimal prefixes from quecto (10⁻³⁰) to quetta (10³⁰), including binary prefixes (kibi, mebi, gibi, etc.).
Unit systems
The five core systems: SI base, SI derived special, SI derived non-special, non-SI acceptable, and non-SI not acceptable.
Getting started
The YAML data files are available in the UnitsDB repository on GitHub. For Ruby developers, the unitsdb-ruby gem provides programmatic access to the database.
You can also browse every entity interactively on the UnitsDB browser.
What's next
UnitsDB 1.0 is the foundation. We are already working on UnitsDB 2.0, which will bring multilingual names, enhanced symbol representations, organization-neutral identifiers, and many new entities.